A practical moving-slit radiographic device with multiple slits, designed primarily for chest radiography, will be constructed. Its performance characteristics, including its effects on radiographic contrast and radiation exposure requirements will first be tested using physical and anatomic phantoms. Preliminary work has indicated that the moving-slit technique at 150 KVp will provide both improved contrast and reduced radiation exposure as compared to conventional chest radiography at 80-120 KVp. The device will then be evaluated clinically in a study of patients at risk for nodular lung disease, including patients with primary cancer known to metastasize to lung, and older male smokers. The efficacy of moving-slit radiography will be assessed and compared to conventional radiographic techniques in terms of lesion detectability, sensitivity, specificity, and predictive value of positive and negative results. Additional second and third year objectives include the design, construction, and evaluation of moving-slit systems usable for radiography on other parts of the body, e.g. the abdomen, and for tomography.